Diblock polymers consisting of a poly(1,3-cyclohexadiene) block and a random copolymer block based on ethylene and a 1,3-diene.

Abstract

The invention relates to a diblock polymer of formula AB, the symbol A representing a thermoplastic block which is a poly(1,3-cyclohexadiene) of number-average molar mass greater than 2000 g / mol and less than 40000 g / mol, the symbol B representing an elastomer block which is a statistical copolymer comprising units of a 1,3-diene and more than 50 mole percent of ethylene units, the 1,3-diene being an α-olefin, in particular 1,3-butadiene.

Description

Title of the invention: Diblock polymers consisting of a poly(1,3-cyclohexadiene) block and a statistical copolymer block based on ethylene and a 1,3-diene.

[0001] The field of the invention is that of diblock polymers containing a thermoplastic hydrocarbon polymer block and an ethylene-rich diene statistical elastomer block.

[0002] Statistical 1,3-diene and ethylene elastomers containing more than 50 mole percent ethylene units are known in the prior art, particularly in the field of tire treads. To modify the properties of these elastomers, it has been proposed to form diblocks by introducing a thermoplastic block at one end of these elastomers, as described, for example, in documents WO 2019077235 and WO 2021123590. The introduction of a thermoplastic block such as polystyrene increases the low-strain moduli of the elastomer. However, it also results in a significant decrease in the elastomer's plasticity, which can be a disadvantage, particularly in elastomer forming operations. There is therefore a need to improve the plasticity of block polymers containing a thermoplastic block and a statistical diene elastomer block rich in ethylene.

[0003] The inventors discovered that the introduction of a thermoplastic poly(l,3-cyclohexadiene) block with a number-average molar mass greater than 2000 g / mol and less than 40000 g / mol into an ethylene-rich diene elastomer instead of a polystyrene block makes it possible to obtain a diblock polymer exhibiting better plasticity than the diblock containing a polystyrene block.

[0004] A first object of the invention is a diblock polymer of formula AB, the symbol A representing a thermoplastic block which is a poly(1,3-cyclohexadiene) with a number-average molar mass greater than 2000 g / mol and less than 40000 g / mol, the symbol B representing an elastomer block which is a statistical copolymer comprising units of a 1,3-diene and more than 50% by mole of ethylene units, the 1,3-diene being an α-olefin.

[0005] A second object of the invention is a composition comprising a dibloc polymer according to the invention and another ingredient. Description of the implementation methods

[0006] Any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​greater than "a" and less than "b" (i.e., excluding bounds a and b), while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from "a" to "b" (i.e. including the strict bounds a and b).

[0007] The compounds mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of materials already used, that is to say, they may be partially or totally derived from a recycling process, or obtained from raw materials themselves derived from a recycling process.

[0008] The block represented by the symbol B in formula AB represents an elastomer block containing ethylene units and units of a 1,3-diene. The elastomer block is a statistical copolymer, meaning that the monomer units constituting the elastomer block are statistically distributed within the block. The block represented by the symbol A is a thermoplastic polymer, a homopolymer of 1,3-cyclohexadiene, also known as poly(1,3-cyclohexadiene).

[0009] In a known manner, an ethylene unit is understood to be a unit having the motif -(CH2-CH2)-. The ethylene units present in the elastomer block represent more than 50% by mole of the monomer units constituting the elastomer block. In the present application, the proportion of ethylene units in the elastomer block, namely the number of moles of ethylene units in the elastomer block, is expressed as a mole percentage relative to the number of moles of monomer units constituting the elastomer block.

[0010] According to any one of the embodiments of the invention, the elastomer block is preferably a statistical copolymer of ethylene and a 1,3-diene, in which case the monomer units of the elastomer block are those resulting from the copolymerization of ethylene and 1,3-diene and are statistically distributed in the elastomer block.

[0011] The 1,3-diene whose monomeric units constitute the elastomer block is an α-olefin. As is known, an α-olefin is an olefin having a terminal double bond and is therefore distinct from 1,3-cyclohexadiene. "One 1,3-diene" means one or more 1,3-dienes, that is, at least two 1,3-dienes. The 1,3-diene is preferably 1,3-butadiene or isoprene, or a mixture of 1,3-dienes, one of which is 1,3-butadiene. More preferably, the 1,3-diene is 1,3-butadiene. Most preferably, the elastomer block is a random copolymer of ethylene and 1,3-butadiene.

[0012] In a known manner, a 1,3-diene can insert itself into a growing polymer chain by a 1,4 or 2,1 or even 3,4 insertion in the case of substituted diene such as isoprene to give rise respectively to the formation of 1,3-diene units of configuration 1,4, 1,3-diene units of configuration 1,2 or of configuration 3,4. Preferably, the 1,3-diene units in the 1,2 configuration and the 1,3-diene units in the 3,4 configuration represent more than 50% by mole of the 1,3-diene units.

[0013] According to one embodiment of the invention, the elastomer block contains 1,3-diene units of configuration 1,4, preferably α-trans. Preferably, the 1,3-diene units of configuration 1,4-trans represent more than 50% by mole of the 1,3-diene units of configuration 1,4. More preferably, the 1,3-diene units of configuration 1,4-trans represent 100% by mole of the 1,3-diene units of configuration 1,4.

[0014] According to a particularly preferred embodiment of the invention, the elastomer block contains units of 1,3-diene which are more than 50% by mole of 1,2 or 3,4 configuration units, the complement to 100% of the 1,3-diene units being 1,4-trans configuration units.

[0015] According to another particularly preferred embodiment of the invention, especially when the 1,3-diene is 1,3-butadiene or a mixture of 1,3-dienes, one of which is 1,3-butadiene, the elastomer block further contains 1,2-cyclohexane or 1,4-cyclohexane motifs, preferably 1,2-cyclohexane motifs. The presence of these cyclic structures in the elastomer block results from a very specific insertion of ethylene and 1,3-butadiene during their copolymerization. The mechanism for obtaining such a microstructure is described, for example, in Macromolecules 2009, 42, 3774-3779. The content of the 1,2-cyclohexane and 1,4-cyclohexane motifs in the elastomer block varies according to the respective contents of ethylene and 1,3-butadiene in the elastomer block. Preferably, it is less than or equal to 15%, a molar percentage expressed relative to the number of moles of monomer units constituting the elastomer block.The elastomer block typically contains less than 10 mole percent of the 1,2-cyclohexane and 1,4-cyclohexane repeating units at the highest ethylene content levels, and may contain more than 10 mole percent at the lowest ethylene content levels, for example up to 15 percent. This percentage is expressed relative to the number of moles of monomer units constituting the elastomer block. The 1,2-cyclohexane repeating unit corresponds to the following formula. CH- CH

[0016] Since the stiffness of the diblock polymer increases with the proportion of ethylene units in the elastomer block, a diblock polymer with a particularly high proportion of ethylene units in the elastomer block may be sought for applications where high material stiffness is required. Preferably, the ethylene units in the elastomer block represent at least 60 mole percent of the units constituting the elastomer block, in which case the elastomer block comprises at least 60 mole percent of ethylene units. Preferably, the ethylene units in the elastomer block represent at most 85 mole percent of the units constituting the elastomer block, in which case the elastomer block contains at most 85 mole percent of ethylene units.

[0017] Preferably, the elastomer block has a glass transition temperature (Tg) below -10°C, preferably between -90°C and -10°C. More preferably, the glass transition temperature of the elastomer block is between -70°C and -20°C, advantageously between -50°C and -20°C. The glass transition temperature of the elastomer block can be adjusted, for example, by the chemical structure of 1,3-diene, with the respective proportions of ethylene units and 1,3-diene units in the elastomer block. The elastomer block has a number-average molar mass preferably greater than or equal to 50,000 g / mol. The elastomer block has a number-average molar mass preferably less than or equal to 150,000 g / mol. According to a preferred embodiment of the invention, the elastomer block has a number-average molar mass greater than or equal to 50,000 g / mol and less than or equal to 150,000 g / mol. According to another preferred embodiment of the invention, the elastomer block has a number-average molar mass ranging from 50,000 g / mol to 100,000 g / mol.

[0018] The thermoplastic block represented by the symbol A in formula AB has the essential characteristic of being a poly(1,3-cyclohexadiene) with a number-average molar mass greater than 2000 g / mol and less than 40000 g / mol. Preferably, the thermoplastic block has a number-average molar mass greater than 5000 g / mol. Preferably, the thermoplastic block has a number-average molar mass less than 30000 g / mol. Even more preferably, the thermoplastic block has a number-average molar mass greater than 5000 g / mol and less than 30000 g / mol.

[0019] The thermoplastic block preferably has a glass transition temperature above 120°C. A glass transition temperature of the thermoplastic block above 120°C gives the diblock polymer better thermal resistance of the polymer properties when exposed to temperatures exceeding 100°C. More preferably, the thermoplastic block has a glass transition temperature above 140°C.

[0020] The dibloc polymer has a number-average molar mass (Mn) preferably between 50,000 g / mol and 200,000 g / mol, more preferably from 60,000 g / mol to 150,000 g / mol, in particular from 60,000 g / mol to 100,000 g / mol.

[0021] The diblock polymer according to the invention can be prepared by a process which comprises the sequence of steps a), b), c) and d): - step a) being the reaction in a hydrocarbon solvent of an organolithium compound and a multidentate polar agent to form a complex consisting of a multidentate polar agent and an organolithium compound, - step b) being the anionic polymerization of 1,3-cyclohexadiene initiated by the complex consisting of a polar multidentate agent and an organolithium compound in a hydrocarbon solvent, to form a poly(l,3-cyclohexadienyl)lithium, - step c) being the reaction between the poly(l,3-cyclohexadienyl)lithium and a halide of an organomagnesium of formula (I) to form an organomagnesium compound of formula R-Mg-A, R-Mg-X (I) R comprising a benzene ring of which two carbon atoms are substituted, one of the two is substituted by a methyl, an ethyl or an isopropyl or forms a ring with the carbon atom which is its nearest neighbor, the second carbon atom being substituted by a methyl, an ethyl or an isopropyl, the magnesium atom being in ortho position with respect to each of said two carbon atoms, X being a halogen atom, A representing a poly(1,3-cyclohexadiene) polymer chain, - step d) being the statistical polymerization of a monomer mixture containing ethylene and 1,3-diene, in the presence of a catalytic system comprising a metallocene of formula (II) and the organomagnesium compound of formula R-Mg-A, P(Cp1Cp2)Nd(BH4)(1+y>Ly-Nx (II) Cp1 and Cp2, identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, Pending a group bridging the two groups Cp1 and Cp2, and comprising a silicon or carbon atom, L represents an alkali metal chosen from the group consisting of lithium, sodium, and potassium, N representing a molecule of an ether, x, an integer or not, being equal to or greater than 0, y, an integer, being equal to or greater than 0.

[0022] Step a) consists of preparing a complex of a multidentate polar agent and an organolithium compound by reacting the organolithium compound and the multidentate polar agent in a hydrocarbon solvent. In the complex of the multidentate polar agent and the organolithium compound, the lithium ion is chelated by the multidentate polar agent. For example, it is well known that multidentate polar agents have the property of chelating the lithium ion from organolithium compounds, thereby enhancing the nucleophilicity of the organolithium compounds. Organolithium compounds are commonly defined as compounds consisting of a carbon chain, preferably a hydrocarbon chain, containing a carbon-lithium bond. Organolithium compounds are most commonly alkyllithium compounds. The alkyl group of an alkyllithium compound may contain one or more carbon atoms, that is, at least two. Organolithium compounds are most commonly butyllithium compounds, and even more commonly n-butyllithium compounds. The multidentate polarizing agent is preferably a bidentate polarizing agent such as N,N,N',N'-tetramethylenediamine, 1,2-dipiperidinoethane, 1,4-diazabicyclo[2,2,2]octane (DABCO), and more preferably N,N,N',N'-tetramethylenediamine. Preferably, the ratio of the number of moles of the multidentate polarizing agent to the number of moles of the organolithium compound in step a) is greater than 0.5 and less than 1. Using a ratio both greater than 0.5 and less than 1 is favorable for obtaining a thermoplastic block with a glass transition temperature well above 100°C, particularly above 120°C. Furthermore, the preferred range of the ratio between the number of moles of the multidendate polarizing agent and the number of moles of the organolithium compound in step a) is also favorable for good control of the respective molar masses of the thermoplastic block and the elastomer block. The hydrocarbon solvent in step a) is preferably an aliphatic solvent, more preferably cyclohexane, methylcyclohexane or a mixture thereof.

[0023] Step b) consists of preparing a poly(1,3-cyclohexadienyl)lithium by anionic polymerization of 1,3-cyclohexadiene in a hydrocarbon solvent in the presence of the complex consisting of the polarizing agent and the organolithium compound that was prepared in step a). The complex consisting of the polarizing agent and the organolithium compound acts as an initiator in the polymerization of 1,3-cyclohexadiene. Poly(1,3-cyclohexadienyl)lithium is known to be a homopolymer of 1,3-cyclohexadiene whose polymer chains possess a reactive center with respect to polymerization, in this case a carbon-lithium bond, particularly at the end of the polymer chain. The hydrocarbon solvent in step b) is preferably an aliphatic solvent, more preferably cyclohexane, methylcyclohexane, or a mixture thereof. Advantageously, the hydrocarbon solvent in step b) is the same as that used in step a). The ratio of hydrocarbon solvent to 1,3-cyclohexadiene required for the formation of poly(1,3-cyclohexadienyl)lithium is selected by those skilled in the art according to the desired viscosity of the poly(1,3-cyclohexadienyl) polymer solution. This viscosity depends not only on the concentration of the polymer solution but also on many other factors, such as the length of the poly(1,3-cyclohexadienyl) chains, the intermolecular interactions between the poly(1,3-cyclohexadienyl)lithium chains, and the temperature of the polymer solution. Therefore, those skilled in the art adjust the amount of solvent on a case-by-case basis. The polymerization temperature for forming poly(l,3-cyclohexadienyl)lithium can vary widely. Generally, it is above -20°C and below 80°C. Preferably, it is above 0°C and below 60°C.

[0024] Step c) consists of reacting poly(1,3-cyclohexadienyl)lithium with a halide of an organomagnesium compound of formula R-Mg-X to form an organomagnesium compound of formula R-Mg-A, R comprising a benzene ring with two substituted carbon atoms, one of the two being substituted by a methyl, an ethyl or an isopropyl or forming a ring with the carbon atom which is its nearest neighbor, the second carbon atom being substituted by a methyl, an ethyl or an isopropyl, the magnesium atom being in an ortho position with respect to each of said two carbon atoms, X being a halogen atom, A representing a poly(1,3-cyclohexadiene) polymer chain. The halide of an organomagnesium compound of formula R-Mg-X is preferably of formula (la) in which Ri and R5, identical or different, represent a methyl or an ethyl, R2, R3 and R4, identical or different, being a hydrogen atom or an alkyl, X being a halogen atom. X preferably represents a chlorine atom or a bromine atom, more preferably a bromine atom. Preferably, Ri and R5 each represent a methyl group. Preferably, R2 and R4 each represent a hydrogen atom. Advantageously, Ri and R5 each represent a methyl group, and R2 and R4 represent each one an atony of hydrogen. Even more advantageously, X represents a bromine atom, Ri and R5 each represent a methyl and R2 and R4 each represent a hydrogen atom. In step c), the reaction between poly(l,3-cyclohexadienyl)lithium and the halide of an organomagnesium compound can be carried out by adding the polymer solution obtained at the end of step b) to a solution of the halide of an organomagnesium compound R-Mg-X, but it is carried out preferentially by adding a solution of the halide of an organomagnesium compound R-Mg-X to the polymer solution obtained at the end of step b). The solution of the halide of an organomagnesium compound R-Mg-X is generally a solution in an ether, preferably diethyl ether or dibutyl ether. The concentration of poly(l,3-cyclohexadienyl)lithium is preferentially from 0.001 to 1 mol of lithium equivalent / L, more preferably from 0.01 to 0.2 mol of lithium equivalent / L, that of the solution of the organomagnesium R-Mg-X preferentially from 1 to 5 mol / L, more preferably from 2 to 3 mol / L.The reaction between poly(1,3-cyclohexadienyl)lithium and the halide of an organomagnesium compound R-Mg-X is typically carried out at a temperature ranging from 0°C to 60°C. Contact is preferably made at a temperature between 0°C and 23°C. As with any synthesis carried out in the presence of organometallic compounds, contact and the reaction take place under anhydrous conditions in an inert atmosphere. Typically, solvents and solutions are used under anhydrous nitrogen or argon. The various steps of the process are generally carried out with stirring. Once formed and without being separated from the reaction medium of step c), the organomagnesium of formula R-Mg-A can be stored in airtight containers, for example capped bottles, at a temperature between -25°C and 23°C, under an inert and anhydrous atmosphere, before it is used in step d).

[0025] Step d) consists of forming a statistical copolymer block comprising 1,3-diene units and more than 50 mole percent ethylene units. Step d) is the statistical polymerization of a monomer mixture containing ethylene and 1,3-diene in the presence of a catalytic system (or catalytic composition) comprising a metallocene and the reaction product of step c), in this case the organomagnesium compound of formula R-Mg-A. The organomagnesium compound of formula R-Mg-A obtained in step c) is used as a cocatalyst for the catalytic system in step d). It is generally used in step d) without being separated from the reaction medium of step c). The metallocene used in the catalytic system has the formula (II) P(Cp1Cp2)Nd(BH4)(1+y>Ly-Nx (II) Cp1 and Cp2, identical or different, being chosen from the group consisting of fluorenyl groups, cyclopentadienyl groups and indenyl groups, the groups being substituted or unsubstituted, Pending a group bridging the two groups Cp1 and Cp2, and comprising a silicon or carbon atom, L represents an alkali metal chosen from the group consisting of lithium, sodium, and potassium, N representing a molecule of an ether, x, an integer or not, being equal to or greater than 0, y, an integer, being equal to or greater than 0.

[0026] In formula (II), the neodymium atom is bonded to a ligand molecule consisting of two groups, Cp1 and Cp2, linked by the P-bridge. Preferably, the symbol P, designated as the bridge, has the formula ZR'R2, where Z represents a silicon or carbon atom, and R1 and R2, which may be identical or different, represent an alkyl group comprising from 1 to 20 carbon atoms, preferably methyl. More preferably, the P-bridge has the formula SiR*R2, where R1 and R2 are identical and as defined above. Even more preferably, P has the formula SiMe2.

[0027] Examples of substituted cyclopentadienyl and fluorenyl groups include those substituted by alkyl groups having 1 to 6 carbon atoms, or by aryl groups having 6 to 12 carbon atoms, or by trialkylsilyl groups such as SiMe3. The choice among alkyl, aryl, and trialkylsilyl groups is also guided by the accessibility of the corresponding molecules, namely the substituted cyclopentadienes and fluorenes, because the latter are commercially available or easily synthesized.

[0028] Examples of substituted cyclopentadienyl groups include those substituted at position 2 (or 5) as well as at position 3 (or 4), particularly those substituted at position 2, more specifically the tetramethylcyclopentadienyl group. In the present application, in the case of the cyclopentadienyl group, position 2 (or 5) refers to the position of the carbon atom adjacent to the carbon atom to which the P-bridge is attached, as shown in the diagram below.

[0029] Examples of substituted fluorenyl groups include those substituted at positions 2,7, 3, or 6, particularly the 2,7-ditertiobutyl-fluorenyl and 3,6-ditertiobutyl-fluorenyl groups. Positions 2, 3, 6, and 7 respectively designate the positions of the carbon atoms in the rings as shown in the diagram below, with position 9 corresponding to the carbon atom to which the P-bridge is attached.

[0030] Preferably, Cp1 and Cp2 are chosen from the group consisting of substituted fluorenyl groups and the unsubstituted fluorenyl group of formula C[3H8]. More preferably, Cp1 and Cp2 are identical and are chosen from the group consisting of substituted fluorenyl groups and the fluorenyl group. Advantageously, in formula (I), Cp1 and Cp2 each represent a substituted fluorenyl group or a fluorenyl group, preferably a fluorenyl group. The fluorenyl group has the formula C[3H8.

[0031] Preferably, the metallocene has the formula (11-1), (II-2), (II-3), (11-4) or (11-5): [Me2Si(Flu)2Nd(p-BH4)2Li(THF)] (11-1) [ {Me2SiFlu2Nd(p-BH4)2Li(THF)}2] (11-2) [Me2SiFlu2Nd(p-BH4)(THF)] (11-3) [{Me2SiFlu2Nd(p-BH4)(THF)}2] (11-4) [Me2SiFlu2Nd(p-BH4)] (11-5) the symbol Flu representing the group Ci3H8.

[0032] The metallocene used to prepare the catalytic system may be in the form of a crystalline or non-crystalline powder, or in the form of single crystals. The metallocene may be in monomeric or dimeric form, these forms depending on the method of preparation of the metallocene, as described, for example, in patent application WO 2007054224. The metallocene may be prepared conventionally by a process analogous to that described in patent application WO 2007054224, in particular by reacting, under inert and anhydrous conditions, the salt of an alkali metal of the ligand with a rare-earth borohydride in a suitable solvent, such as an ether, like diethyl ether or tetrahydrofuran, or any other solvent known to those skilled in the art. After the reaction, the metallocene is separated from the reaction byproducts by techniques known to those skilled in the art, such as filtration or the precipitation in a second solvent. The metallocene is then dried and isolated in solid form.

[0033] As with any synthesis carried out in the presence of an organometallic compound, the synthesis of metallocene takes place under anhydrous conditions in an inert atmosphere. Typically, the reactions are conducted using solvents and anhydrous compounds under anhydrous nitrogen or argon.

[0034] The catalytic system can be prepared conventionally by a process analogous to that described in patent application WO 2007054224 or WO 2007054223. For example, the co-catalyst and the metallocene are reacted in a hydrocarbon solvent, typically at a temperature of 20 to 80°C for a time of 5 to 60 minutes. The amounts of co-catalyst and metallocene reacted are such that the ratio of the number of moles of Mg in the co-catalyst to the number of moles of rare-earth metal in the metallocene is preferably from 1 to 100, and more preferably from 1 to less than 10. The range of values ​​from 1 to less than 10 is particularly favorable for obtaining polymers with high molar masses. The catalytic system is usually prepared in a hydrocarbon solvent, aliphatic such as methylcyclohexane or aromatic such as toluene.Generally, after its synthesis, the catalytic system is used as is in the polymer synthesis process according to the invention.

[0035] The catalytic system is generally in the form of a solution in a hydrocarbon solvent. The hydrocarbon solvent can be aliphatic, such as methylcyclohexane, or aromatic, such as toluene. The hydrocarbon solvent is preferably aliphatic, and more preferably methylcyclohexane. Generally, the catalytic system is stored as a solution in the hydrocarbon solvent before being used in polymerization. This can then be referred to as a catalytic solution, which comprises the catalytic system and the hydrocarbon solvent. The concentration of the catalytic solution is typically defined by the metallocene content in the solution. The metallocene concentration preferably ranges from 0.0001 to 0.2 mol / L, and more preferably from 0.001 to 0.03 mol / L.

[0036] As with any synthesis carried out in the presence of an organometallic compound, the synthesis of the catalytic system takes place under anhydrous conditions in an inert atmosphere. Typically, the reactions are conducted using solvents and anhydrous compounds under anhydrous nitrogen or argon.

[0037] The catalytic system is generally introduced into the reactor containing the polymerization solvent and the monomer mixture containing ethylene and 1,3-diene. To achieve the desired macrostructure of the statistical copolymer block, those skilled in the art adjust the polymerization conditions, in particular the ratio molar ratio of magnesium co-catalyst to Nd metal constituting the metallocene. The molar ratio can reach a value of 100, knowing that a molar ratio less than 10 is more favorable for obtaining polymers with high molar masses.

[0038] In step d), the monomer mixture containing ethylene and 1,3-diene generally contains more than 50 mol% ethylene and is preferably a mixture of ethylene and 1,3-diene, in which case the block represented by the symbol B is a statistical copolymer of ethylene and 1,3-diene, in other words, a block whose constituent monomer units are those resulting from the statistical copolymerization of ethylene and 1,3-diene. Preferably, the monomer mixture containing ethylene and 1,3-diene contains less than 90 mol% ethylene. More preferably, the monomer mixture containing ethylene and 1,3-diene contains at most 85 mol% ethylene.

[0039] Preferably, a continuous addition of ethylene and 1,3-diene is carried out in the polymerization reactor, in which case the polymerization reactor is a fed reactor. This embodiment is particularly suitable for the statistical incorporation of ethylene and 1,3-diene.

[0040] The polymerization temperature generally varies in the range of 30 to 160°C, preferably from 30 to 120°C. During the preparation of the statistical copolymer block, the temperature of the reaction medium is advantageously kept constant during copolymerization, and the total pressure in the reactor is also advantageously kept constant. The preparation of the statistical copolymer block is completed by stopping the monomer feed and then degassing the reactor to reduce the reactor pressure to approximately 0 to 0.5 bar (relative).

[0041] At the end of step d), the polymerization is stopped by deactivating the active polymerization sites, for example by cooling the polymerization medium or by adding an alcohol, preferably an alcohol containing 1 to 3 carbon atoms, for example ethanol. The diblock polymer can be recovered using conventional techniques known to those skilled in the art, such as precipitation, evaporation of the solvent under reduced pressure, or steam stripping.

[0042] Advantageously, the sequence of steps a), b), c), d) is carried out without separating the reaction products of each of the intermediate steps, namely steps a), b), c) and, where applicable, d). The polymerizations of steps a), b), c), d) can be carried out continuously or discontinuously.

[0043] The diblock polymer according to the invention can be used in a composition, another object of the invention, which typically comprises another ingredient. The other ingredient may be a filler such as carbon black or silica, a plasticizer such as oil, a crosslinking agent such as sulfur or peroxide, an agent antioxidant, or a polymer other than the dibloc polymer according to the invention. The composition may be a rubber composition.

[0044] In summary, the invention is preferably implemented according to any one of the following embodiments 1 to 18:

[0045] Mode 1: Diblock polymer of formula AB, the symbol A representing a thermoplastic block which is a poly(l,3-cyclohexadiene) of number-average molar mass greater than 2000 g / mol and less than 40000 g / mol, the symbol B representing an elastomer block which is a statistical copolymer comprising units of a 1,3-diene and more than 50% by mole of ethylene units, the 1,3-diene being an α-olefin.

[0046] Mode 2: Diblock polymer according to mode 1 in which the elastomer block comprises at most 85 mole percent of ethylene units.

[0047] Mode 3: Diblock polymer according to mode 1 or 2 in which the elastomer block comprises at least 60 mole percent of ethylene units.

[0048] Mode 4: Diblock polymer according to any one of modes 1 to 3 in which the elastomer block is a statistical copolymer block of ethylene and a 1,3-diene.

[0049] Mode 5: Diblock polymer according to any one of modes 1 to 4 in which the 1,3-diene is 1,3-butadiene or isoprene or a mixture of 1,3-dienes of which one is 1,3-butadiene.

[0050] Mode 6: Diblock polymer according to any one of modes 1 to 5 in which the 1,3-diene is 1,3-butadiene.

[0051] Mode 7: Diblock polymer according to any one of modes 1 to 6 in which the elastomer block is a random copolymer of ethylene and 1,3-butadiene.

[0052] Mode 8: Diblock polymer according to mode 6 or 7 in which the elastomer block further contains 1,2-cyclohexane motifs or 1,4-cyclohexane motifs, preferably 1,2-cyclohexane motifs.

[0053] Mode 9: Diblock polymer according to mode 8 in which the content of 1,2-cyclohexane motif and 1,4-cyclohexane motif of the elastomer block is less than or equal to 15%, molar percentage expressed in relation to the number of moles of monomer units constituting the elastomer block.

[0054] Mode 10: Diblock polymer according to any one of modes 1 to 9 in which the elastomer block has a number-average molar mass greater than or equal to 50000 g / mol.

[0055] Mode 11: Diblock polymer according to any one of modes 1 to 10 in which the elastomer block has a number-average molar mass less than or equal to 150000 g / mol.

[0056] Mode 12: Diblock polymer according to any one of modes 1 to 11 in which the thermoplastic block has a number-average molar mass greater than 5000 g / mol.

[0057] Mode 13: Diblock polymer according to any one of modes 1 to 12 in which the thermoplastic block has a number-average molar mass of less than 30000 g / mol.

[0058] Mode 14: Diblock polymer according to any one of modes 1 to 13 in which the thermoplastic block has a glass transition temperature greater than 120°C.

[0059] Mode 15: Diblock polymer according to any one of modes 1 to 14 in which the thermoplastic block has a glass transition temperature greater than 140°C.

[0060] Mode 16: Diblock polymer according to any one of modes 1 to 15 which has a number-average molar mass between 50,000 g / mol and 200,000 g / mol.

[0061] Mode 17: Diblock polymer according to any one of modes 1 to 16 which has a number-average molar mass ranging from 60,000 g / mol to 150,000 g / mol.

[0062] Mode 18: Composition comprising a diblock polymer according to any one of modes 1 to 17 and another ingredient.

[0063] The aforementioned features of the present invention, as well as others, will be better understood upon reading the following description of several examples of embodiments of the invention, given by way of illustration and not limitation. Examples

[0064] The designation EBR is used to denote a statistical copolymer of ethylene and 1,3-butadiene; the designation PCHD is used to denote a homopolymer of 1,3-cyclohexadiene; the designation PS is used to denote a homopolymer of polystyrene; the designation Mes is used to denote the mesityl group. Size exclusion chromatography (SEC-THF):

[0065] Size-exclusion chromatography analyses of polystyrene homopolymers and PS- / »-EBR diblock polymers were performed using a Viscotek TDmax instrument (Malvem Instruments) equipped with a guard column and three columns (SDVB, 5 µm, 330 x 7.5 mm, Polymer Standards) and three detectors (refractometer, viscometer, and light scatterer). Samples were prepared at a concentration of 3–4 mg mL in THF and filtered through a 0.45 µm PTFE membrane. Analyses were performed at 40 °C in stabilized THF at a flow rate of 1 mL min*. Data were acquired and processed using OmniSEC 5.02 software. The number-average molar masses (Mn) of the copolymers were determined using conventional calibration obtained from polystyrene standards (800–2,500,000 g mol⁻¹), Polymer Standard Service (Mainz), using a refractometer detector. The dispersity D (D = Mw / Mn) was also determined.

[0066] Size exclusion chromatography (SEC-HT): Size-exclusion chromatography analyses of the entire PCHD group and the PCHD-Zα-EBR diblock copolymers were performed using a Tosoh Bioscience Instrument (HLC-8321-GPC (HT-GPC)) equipped with two columns (TSKgel ultra-high-temperature columns with mixed pore size) and coupled to a refractometer detector. The exclusion limit of the columns was 4.0 x 10⁸ Da. Samples were prepared at a concentration of 3–5 mg mL⁻¹ in 1,2,4-trichlorobenzene. The columns and detectors were maintained at 150°C. Sample volumes of 100 pL were injected and eluted with 1,2,4-trichlorobenzene (TCB) at a flow rate of 1 mL min⁻¹ at 150°C. The mobile phase was stabilized with 2,6-di(tert-butyl)-4-methylphenol (BHT) (0.2 g L').The dispersity D (D = MJ M^) and the number-average and mass-average molar masses (Mn and Mw respectively) of the polymers were determined from a conventional calibration using polystyrene standards with Tosoh's GPC Analysis software for data acquisition.

[0067] Differential scanning calorimetry (DSC): DSC analyses are performed on a DSC 3+ instrument (Mettler Toledo) with sealed aluminum crucibles (40 pL) and under a nitrogen flow (30 mL min⁻¹). The temperature programs are as follows:

[0068] The thermograms of the PCHDs are obtained according to the following program: * step 1: ramp from 25 °C to 220 °C (10 °C min '), • step 2: isothermal at 220 °C for 5 min, * step 3: ramp from 220 °C to -80 °C (10 °C min '), • step 4: isothermal at -80 °C for 5 min, * step 5: ramp from -80 °C to 220 °C (10 °C min '), • step 6: isothermal at 220 °C for 5 min, * step 7: ramp from 220 °C to -80 °C (10 °C min '), • step 8: isothermal at -80 °C for 5 min, * step 9: ramp from -80 °C to 220 °C (10 °C min '). The glass transition temperatures (Tg) of the PCHDs reported in Table 1 were determined in step 5 (ramp -80 °C to 220 °C at 10 °C min').

[0069] The thermogram of the PCHD-Z-EBR diblock copolymer (Example 1) is obtained according to the following program: * step 1: ramp from 25 °C to 220 °C (10 °C min'), • step 2: isothermal at 220 °C for 5 min, * step 3: ramp from 220 °C to -80 °C (10 °C min'), • step 4: isothermal at -80 °C for 5 min, * step 5: ramp from -80 °C to 220 °C (10 °C min'), • step 6: isothermal at 220 °C for 5 min, * step 7: ramp from 220 °C to -80 °C (10 °C min'), • step 8: isothermal at -80 °C for 5 min, * step 9: ramp from -80 °C to 220 °C (10 °C min *). The glass transition temperatures (Tg) of the EBR blocks reported in Table 1 were determined in step 5 (ramp -80 °C to 220 °C at 10 °C min1).

[0070] The thermogram of the PS- / ?-EBR diblock copolymer (example 2) is obtained according to the following program: • step 1: ramp from 25 °C to 180 °C (10 °C min '), • step 2: isothermal of 5 min at 180 °C, • step 3: ramp from 180 °C to -80 °C (10 °C min 1 ), • step 4: isothermal of 5 min at -80 °C, • step 5: ramp from -80 °C to 180 °C (10 °C min '), • step 6: isothermal of 5 min (180 °C), • step 7: ramp from 180 °C to -80 °C (10 °C min '), • step 8: isothermal of 5 min at -80 °C • step 9: ramp from -80 °C to 180 °C (10 °C min '). The glass transition temperatures (Tg) and melting temperatures (Tf) of the EBR and PE blocks respectively reported in Table 1 were determined in step 9.

[0071] Tensile tests: Tensile testing is performed on an MTS Criterion C42 tensile tester at the temperature of the sample being analyzed (20-25°C), equipped with a 50 N load cell and a cross-sectional speed of 500 mm / min. The materials are pressed at 150°C under 4-5 tons in an 80 mm x 60 mm x 1.5 mm mold. Standard H2 type specimens (usable dimensions 30 mm x 4 mm) are cut at room temperature using a suitable die. Polymer preparation:

[0072] All reactions sensitive to air and / or humidity are carried out under an argon atmosphere. 2-Methyltetrahydrofuran (MeTHF) was distilled over sodium / benzophenone. The dry polymerization solvents (methylcyclohexane and cyclohexane) were collected from the solvent fountain (SPS800 MBraun). The cyclohexane was stored in a glove box on a molecular sieve (3 Å) before use. 1,3-Cyclohexadiene (abcr) is dried for 24 hours on CaH2 under an argon atmosphere and then distilled under vacuum. Styrene (Sigma-Aldrich) is also dried for 24 hours on CaH2 under an argon atmosphere and then distilled under vacuum. Ethylene (grade N35, Air Liquide) is used without purification. 1,3-Butadiene, previously purified on an Axens alumina purification column and stabilized with 60 ppm TBC, is purified by contact with trioctylaluminium for 30 minutes before use. n-Butyllithium (1.6M in hexane, Sigma-Aldrich) is used as received. Tetramethylethylenediamine (TMEDA) is dried for 24 h on CaH2 under an argon atmosphere, then distilled under vacuum and stored on a molecular sieve (3 Å). The {Me2Si(Ci3H8)2Nd(BH4)2Li(THF)}2 complex is prepared according to the protocol described in patent application WO 2007054224 A2. 2,2'-Methylenebis(6-tert-butyl-4-methylphenol) (di-BHT, Sigma-Aldrich) is used as received as an antioxidant. Acetone (technical grade) is used to precipitate the polymers. The reactor used in steps 2 is a 250 mL glass reactor equipped with a stirring wheel (anchor).

[0073] Commercial 2-mesityl-magnesium bromide (BMM, IM in Et2O, Sigma-Aldrich) is used as received.

[0074] Synthesis of 2-mesityl-magnesium bromide (BMMMeTHF, 0.5 M in toluene)

[0075] In a 100 mL round-bottom flask, a magnesium suspension (4.15 g, 3.4 equivalents) is activated with 30 mg of I₂ in 10 mL of MeTHF. A solution of 2-bromomesitylene (7.65 mL, 50 mmol) in 40 mL of MeTHF is added dropwise to this suspension with vigorous stirring. The temperature is set at 35–40°C. After two hours of reaction, the solution is filtered, and the solvent is evaporated, yielding an oily product (21.58 g). 1H NMR confirms the formation of MesMgBr with a MeTHF / Mg ratio of 2.7. The product is solubilized in toluene to obtain a concentration of 0.5 M.

[0076] Example 1 according to the invention: PCHD-Z-EBR diblock polymer, PCHD mass fraction being 0.26:

[0077] Step 1: Anionic polymerization of 1,3-cyclohexadiene and preparation of the organomagnesium compound of formula PCHD-MgMes: In a conditioned Schlenk tube (3 vacuum-argon cycles), 25 mL of cyclohexane (msoivant / mmonomer ratio = 7.8), 0.156 mL (0.25 mmol) of n-BuLi (1.6 M in hexane), and 28 µL (0.1875 mmol, 0.75 equivalent) of TMEDA are introduced. The mixture is stirred at 40 °C for 10 min, then 2.5 g of 1,3-cyclohexadiene is added. The solution turns yellow instantly, and the reaction mixture is stirred at 40 °C for 120 min. The transmetallation reaction is then carried out with the addition of 0.3 mL (0.3 mmol, 1.2 equivalents) of BMM to obtain an organomagnesium compound of formula R-Mg-A, where A is a poly(1,3-cyclohexadiene) (PCHD) and R is the mesityl group (Mes). The mixture is then transferred using a cannula under argon flow into the reactor, which has been pre-conditioned and heated to 90 °C.

[0078] Step 2: Formation of the PCHD-6-EBR diblock copolymer: 39.4 mg (62 pmol Nd) of the Nd{Me2Si(Ci3H8)2Nd(BH4)2Li(THF)} complex is weighed into a 50 mL glovebox. 175 mL of MCH (VMCh + Vcyciohexane = 200 mL) is taken from the solvent fountain into a 250 mL flask. 0.24 mL (0.24 mmol) of BMM is added to the MCH. The (MCH + BMM) solution is stirred for 5 min, and then the Nd{Me2Si(Ci3H8)2Nd(BH4)2Li(THF)} complex is added. The catalytic solution is transferred using a cannula under argon flow into the reactor already containing the PCHD-MgMes solution. The reactor is isolated and the pressure reduced to 0.5 bar before agitation is started (1000 rpm). The reactor is then pressurized to 4 bar with an ethylene / 1,3-butadiene mixture. with an 80 / 20 molar ratio. The t0 is considered when the medium reaches a temperature of 89 °C. The pressure is maintained constant in the reactor using a reservoir containing the ethylene / 1,3-butadiene mixture, and polymerization is carried out at 90 °C. Monomer consumption is monitored by the pressure drop in the reservoir until the desired consumption is reached. The reactor is then carefully depressurized and degassed under argon flow, and the medium is deactivated by adding EtOH (approximately 0.5 mL) and then cooled to room temperature. The copolymer is then precipitated in 600 mL of acetone before being collected in an aluminum capsule. 50 mL of a 10 g L1 solution of the antioxidant 2,2'-methylenebis(6-tert-butyl-4-methylphenol) (di-BHT) is added to the copolymer, and the solvent is evaporated under vacuum at 70 °C for 7 h. The PCHD-Z?-EBR diblock copolymer is weighed and analyzed.

[0079] Example 2 not in accordance with the invention: PS- / »-EBR diblock polymer, PS mass fraction being 0.27

[0080] Step 1: Anionic polymerization of styrene and preparation of the organomagnesium compound with formula PS-MgMes: In an inert Schlenk tube, 40 mL of dry toluene and 5.5 mL of styrene (5 g, 48 mmol) are introduced. 0.22 mL of ethyl tetrahydrofurfuryl ether (0.3 M in toluene, 0.066 mmol) is added, followed by 0.21 mL of n-BuLi (1.6 M in hexane, 0.33 mmol). The solution turns red. The reaction mixture is stirred at 40 °C for 20 min, and then the transmetallation reaction is carried out with 0.8 mL of BMMMeTHF (0.4 mmol, 1.2 eq.) to obtain a macro-ATC PSi5K-MgMes. An aliquot is taken and precipitated in ethanol. This solution is transferred under argon flow to the previously inert reactor.

[0081] Step 2: Formation of the PS- / »-EBR diblock copolymer: 32 mg (50 pmol Nd) of the Nd{Me2Si(Ci3H8)2Nd(BH4)2Li(THF)]2 complex are weighed into a 50 mL glovebox. 155 mL of toluene is taken from the solvent fountain into a 250 mL flask. 0.40 mL (0.20 mmol) of BMMMeTHF is added to the toluene. The solution is stirred for 5 min before the Nd{Me2Si(Ci3H8)2Nd(BH4)2Li(THF)]2 complex is added. The catalytic solution is transferred using a cannula under argon flow into the reactor already containing the PSi5K-MgMes solution. The reactor is isolated and the pressure reduced to 0.5 bar before starting stirring (1000 rpm). The reactor is then pressurized to 4 bar with an ethylene / l,3-butadiene mixture with an 80 / 20 molar ratio. The temperature t0 is considered to be when the medium has reached 89 °C. The pressure is maintained constant in the reactor using a reservoir containing the ethylene / l,3-butadiene mixture.Monomer consumption is followed by a pressure drop in the tank until the desired consumption is reached. The reactor is then depressurized and degassed. Under argon flow, polymerization is deactivated by adding EtOH (approximately 0.5 mL) and the medium is cooled to room temperature. A few milligrams of the antioxidant 2,2'-methylenebis(6-tert-butyl-4-methylphenol) (di-BHT) are added, and the copolymer is precipitated in 400 mL of MeOH. The polymer is washed with methanol, then collected in a crystallizer and dried under vacuum at 80 °C for 4 h. The dibloc PS-ε-EBR copolymer is weighed and analyzed.

[0082] Example 3 not in accordance with the invention: EBR polymer

[0083] 199 mL of toluene taken from the solvent fountain (SPS800 MBraun) are introduced In an inert 250 mL round-bottom flask fitted with a magnetic stir bar, 0.19 mL of a 0.52 M butylmagnesium solution in heptane is introduced with stirring. 32.0 mg (50 pmol neodymium) of {(Me₂Si(Ci₃H₈)₂)Nd(p-BH₄)[(p-BH₄)Li(THF)]}₂ is then introduced into the flask. The catalytic solution is cannulated into a 250 mL reactor under an inert atmosphere. The pressure in the reactor is reduced to 0.5 bar, and then the reactor is pressurized to 4 bar with an 80 / 20 mol / mol ethylene / butadiene mixture, while the temperature is simultaneously raised to 90 °C. The pressure is maintained constant in the reactor using a reservoir containing an 80 / 20 mol / mol ethylene / butadiene gas mixture. When the desired quantity of monomers has been consumed, here after 12 g, the reactor is carefully depressurized and degassed under a flow of argon, and the medium is deactivated by the addition of EtOH (approximately 0.5 mL) and then cooled to room temperature.0.2 g of antioxidant 2,2'-methylenebis(6-tert-butyl-4-methylphenol) (di-BHT) are added and the copolymer is precipitated in 600 mL of MeOH, then it is recovered in a crystallizer and dried under vacuum at 80-100 °C for 6 h.

[0084] The structure of the prepared polymers is identified by SEC and DSC analysis. The results are shown in Table 1. The Mn and Tg of the PCHD and PS blocks are measured on a sample taken at the end of step 1.

[0085] Table 1: Example Example 1 Example 2 Example 3 Polymer PCHD-EBR PS-EBR EBR Mn thermoplastic block (g / mol), (D) 20300 (1.25) 14700 (1.06) - Tg thermoplastic block 148°C 99 - Mn polymer (g / mol) 79400 53000 60700 (£» (1.46) (1.59) (1.32) Tg EBR block -31°C -33°C -32°C Thermoplastic block 0.26 0.27 0 | (mass fraction)||||

[0086] In Examples 1 and 2, the diblock polymers have a thermoplastic block, respectively HDPE and PS, and an EBR elastomer block, the mass fraction of the thermoplastic block being similar. In Example 3, the polymer is an EBR, the mass fraction of the thermoplastic block then being 0.

[0087] The elongation at break of the PCHD-EBR diblock (Example 1) and the maximum stress applied to it are compared to those of the PS-EBR diblock (Example 2), at the same mass fraction of thermoplastic block in the diblock polymer. The EBR polymer of Example 3 is used in the comparisons as a reference. The results are shown in Table 2.

[0088] Table 2: Dibloc PCHD-EBR PS-EBR EBR Thermoplastic block (mass fraction) 0.26 0.27 0 Elongation at break (%) 410 280 1260 Maximum stress (N / mm²) 0.6 2 0.2

[0089] It is observed that the introduction of a thermoplastic block into the EBR polymer strongly impacts both the maximum stress and the elongation at break of the polymer. However, the introduction of the PCHD block has a lesser impact than that of a PS block. Given the improved elongation at break, PCHD-EBR diblock polymers exhibit better plasticity than their PS-EBR counterparts.

Claims

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11. Demands Diblock polymer of formula AB, the symbol A representing a thermoplastic block which is a poly(l,3-cyclohexadiene) of number-average molar mass greater than 2000 g / mol and less than 40000 g / mol, the symbol B representing an elastomer block which is a statistical copolymer comprising units of a 1,3-diene and more than 50% by mole of ethylene units, the 1,3-diene being an α-olefin. Diblock polymer according to claim 1 in which the elastomer block comprises at most 85 mole percent of ethylene units. Diblock polymer according to claim 1 or 2 in which the elastomer block comprises at least 60 mole percent of ethylene units. Diblock polymer according to any one of claims 1 to 3 wherein the elastomer block is a statistical copolymer block of ethylene and a 1,3-diene. Diblock polymer according to any one of claims 1 to 4 wherein the 1,3-diene is 1,3-butadiene or isoprene or a mixture of 1,3-dienes of which one is 1,3-butadiene. Diblock polymer according to any one of claims 1 to 5 wherein the 1,3-diene is 1,3-butadiene. Dibloc polymer according to any one of claims 1 to 6 wherein the elastomer block has a number-average molar mass greater than or equal to 50000 g / mol. Dibloc polymer according to any one of claims 1 to 7 wherein the elastomer block has a number-average molar mass less than or equal to 150000 g / mol. Dibloc polymer according to any one of claims 1 to 8 wherein the thermoplastic block has a number-average molar mass greater than 5000 g / mol. Dibloc polymer according to any one of claims 1 to 9 wherein the thermoplastic block has a number-average molar mass of less than 30000 g / mol. Diblock polymer according to any one of claims 1 to 10 wherein the thermoplastic block has a glass transition temperature greater than 120°C.

12. Diblock polymer according to any one of claims 1 to 11 wherein the thermoplastic block has a glass transition temperature greater than 140°C.

13. Diblock polymer according to any one of claims 1 to 12 having a number-average molar mass of between 50,000 g / mol and 200,000 g / mol, more preferably from 60,000 g / mol to 150,000 g / mol.

14. Composition comprising a diblock polymer according to any one of claims 1 to 13 and another ingredient.